Neuroprotective Effects of Quercetin and Rutin on Spatial Memory Impairment in an 8-Arm Radial Maze Task and Neuronal Death Induced by Repeated Cerebral Ischemia in Rats

In order to determine the differential effects of flavonoids on cerebral ischemia, we investigated the effects of (−)-epigallocatechin gallate (EGCG), catechin, rutin, and quercetin on spatial memory impairment and neuronal death induced by repeated cerebral ischemia in rats. Both rutin and quercetin (50 mg/kg × 2) improved spatial memory impairment in the 8-arm radial maze task and neuronal death in the hippocampal CA1 area; however, catechin (200 mg/kg × 2) and EGCG (50 mg/kg × 1) did not. Administration of EGCG (50 mg/kg × 2) resulted in a high mortality rate. These results suggest that in this repeated cerebral ischemia model, the 4-oxo group and the 2,3-double bond in the C ring of rutin and quercetin are related to their neuroprotective action.